Fuel nature measuring device of internal combustion engine and internal combustion engine having the same

1. A fuel nature measuring device, for measuring the nature of fuel stored in a fuel tank of an internal combustion engine, the measuring device comprising: a measurement passage having an orifice therein; gas flow generating means for generating a gas flow in said measurement passage; differential pressure detecting means for detecting a differential pressure between opposite ends of said orifice; evaporated fuel concentration operating means for determining a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when said opposite ends of said measurement passage communicates with said fuel tank and the fuel in the fuel tank flows in said measurement passage; temperature detecting means for determining a temperature of the fuel in said fuel tank; volatility calculation means for calculating a volatility of the fuel in said fuel tank as the fuel nature based on the concentration of the evaporated fuel determined by said evaporated fuel concentration operation means and the temperature determined by said temperature detecting means; and measurement passage switching means for switching between first and second concentration measurement states, the first concentration measurement state being configured such that said opposite ends of said measurement passage are opened to the atmosphere and the gas passed through said measurement passage is atmospheric air, the second concentration measurement state being i&-configured such that said opposite ends of said measurement passage communicate with said fuel tank through a gas phase portion of said fuel tank and the fuel flows in said fuel measurement passage is the fuel from the fuel tank, wherein said evaporated fuel concentration operating means determines the concentration of the evaporated fuel based on a difference in detected differential pressures across said measurement passage between said first and second concentration measurement states.

2. The fuel nature measuring device according to claim 1 , further comprising: first valve means for blocking the gas flow through said orifice, said differential pressure detecting means including a pair of lead passages having said orifice and said valve means therebetween; a detection space including said canister defined when said purge control valve is closed and for communicating with said measurement passage on the side of one of said leading passages; a communication passage to allow communicating with said measurement passage on a side of one of said leading passages; second valve means for blocking said communication passage; and leakage determining means for determining the presence of a leakage in said detection space based on values detected by said differential pressure detecting means in a first and a second leakage detection state, the first leakage detection state being configured such that said measurement passage is open and said communication passage is blocked, and the second leakage detection state being configured such that said measurement passage is blocked and said communication passage is open.

3. A method of measuring a nature of fuel stored in a fuel tank of an internal combustion engine, the method comprising: generating a gas flow in a measurement passage having an orifice therein; detecting a differential pressure between opposite ends of said orifice; determining a concentration of evaporated fuel in the fuel tank based on the differential pressure detected when said opposite ends of said measurement passage communicates with said fuel tank and the fuel in the fuel tank flows in said measurement passage; determining a temperature of the fuel in said fuel tank; and calculating a volatility of the fuel in said fuel tank as the fuel nature based on the determined concentration of the evaporated fuel and the determined temperature; switching between first and second concentration measurement states, the first concentration measurement state being configured such that said opposite ends of said measurement passage are opened to the atmosphere and the gas passed through said measurement passage is atmospheric air, the second concentration measurement state being configured such that said opposite ends of said measurement passage communicate with said fuel tank through a gas phase portion of said fuel tank and the fuel flows in said fuel measurement passage is the fuel from the fuel tank, wherein determining the concentration of the evaporated fuel is determined based on a difference in detected differential pressures across said measurement passage between said first and second concentration measurement states.

4. The method according to claim 3 , further comprising: blocking the gas flow through said orifice using a first valve, said detecting the differential pressure being accomplished via a pressure detector which includes a pair of lead passages having said orifice and said first valve therebetween; defining a detection space including said canister defined when said purge control valve is closed and for communicating with said measurement passage on the side of one of said leading passages; providing a communication passage to allow communicating with said measurement passage on a side of one of said leading passages; blocking said communication passage using a second valve; and determining the presence of a leakage in said detection space based on detected differential pressure values in a first and a second leakage detection state, the first leakage detection state being configured such that said measurement passage is open and said communication passage is blocked, and the second leakage detection state being configured such that said measurement passage is blocked and said communication passage is open.